This invention relates to rotatable wing aircraft and more particularly to one in which the wing is unitary in nature and coupled to the fuselage through a large hollow turret, enabling it to be held in either of two positions, a 90 degree position, perpendicular to the fuselage for low speeds, and a 0 degree one, parallel to the fuselage, for high speed flight. Alternatively, the wing could be coupled to the fuselage through a solid pivot pin, but structures would require more weight for the condensed stress areas. At high speeds, the wing is faired into fuselage structure with its upper surface and an overlap portion with winglets cooperating with the lower surface of the fuselage to provide necessary lift. A set of winglets, small moveable aerosurfaces, is built into the center of the wing, each cooperating with the other to provide roll control and lift at high speeds when the wing is parallel with the fuselage. Greatly reduced "wetted" area of the wing is produced by this condition with up to 50 percent of the bottom of the wing nested into the fuselage and with a corresponding reduction in aerodynamic drag of approximately 25 percent.
For low speeds employed during takeoff and landing, the wing is oriented perpendicular to the fuselage, utilizing pivoted winglet type ailerons at either extreme for lift and control torques. Typical winglets comprise about 10 percent of total wing area. At high speeds, the wing is nested parallel to the fuselage, its upper surface contoured to provide lift as required in cooperation with the bottom of the fuselage and overlap beyond the nested area. Winglets extending from both sides of the middle of the wing provide roll control during high speed operation. Computerized winglet control during the transition mode maintains reasonable attitude conditions of the aircraft, while nesting the wing parallel to the fuselage reduces its wetted area by 25 to 30 percent, greatly increasing efficiency of high speed operation. At the low speed, or ninety (90) degree position, a high aspect ratio wing is provided that is more efficient than delta types and which provides more maneuver response than delta wings at such lower speeds.
The National Aeronautics and Space Administration (NASA) has conducted extensive experimentation on oblique wing aircraft wherein a unitary wing (i.e. a single member extending symmetrically about a central chord) is pivoted in flight to form an angle with the fuselage to reduce its wetted area, increase leading edge sweep, and, consequently, reducing its aerodynamic drag. Tests, to be conducted in the late 1989 time period, will provide for pivoting wings at up to 60 degrees for flight at speeds up to Mach 1.4 (about 1000 miles hr). The aircraft scheduled for such tests is known as the Digital Fly-By-Wire (DFBW) test bed, NASA model F-8.
The DFBW has been in use for several years as a flying test platform for electronic, computer operated, flight control systems. Integration of computer controls with wing positioning mechanisms of the within invention will allow for safe transition from one orientation to the other at all speeds, up to, and including, supersonic and at right angles to the conventional wing orientation, as opposed to DFBW's 60 degree inclination.
Rotation of the wing from its 0 degree, high speed orientation to the 90 degree condition will provide the craft augmented "post-stall" or "super-maneuvering" capability by reason of the 90 degree condition's greater lift, higher drag and lower stall speed. Such capability provides escape potential and attack maneuver capability considerably exceeding that of conventional delta or double delta winged vehicles.
Many advantages accrue from use of the unitary, rotatable wing presented herein. High lift provided with the wing rotated 90 degrees from the fuselage allows slower speeds for takeoff and landing with associated shorter runways. The slower speeds and increased lift requires lighter weight landing gear and shock structure. Angles of approach to runways can be steeper for the reduced speeds involved and pilots are afforded greater visibility over the nose of the aircraft.
Use of such an airplane for fleet support on aircraft carriers is particularly beneficial. After landing with the wing at its high lift position, the craft is hangared and moved with that wing stowed parallel to the fuselage at significant economies in volume required, a prime concern of naval vessels.
Primary advantage of the 90 degree rotation wing is the greatly reduced frictional drag when the plane is performing at high speeds. 25 to 30 percent of the normally "wetted" area of the wing is hidden over the fuselage when it, the wing, is in the 0 degree orientation.
Because of the wing's unitary nature, enhanced use of internal volumes for fuel storage or other purposes is provided. Conventional or swing wing craft exhibit discontinuities at their interfaces with craft structure with complicated strengthening provisions often made which intrude into the wing and fuselage structure. In the 90 degree rotatable wing, flexible fuel and hydraulic lines provide optimal reliability with no "moving parts" for junctions or moveable joints and a large turret connector between wing and fuselage provides a simple, highly reliable support for rapid, low energy transfer between the 0 degree high speed, low friction, and 90 degree, low speed, high lift positions.
Since the connecting turret between wing and fuselage of this craft will have extensive bearing surfaces and possibly air bearings for reduced friction in transit, greatly enhanced maneuverability in air to air combat situations can be achieved by transfer of the wing from its 0 degree, high speed, position, to the 90 degree, low speed, high lift condition. Preliminary studies indicate that such a change in wing positioning can be effected at supersonic speeds with resultant high decelerations and vertical lift vectoring. Such maneuvers may be critical in evading high speed missiles with less maneuverability. Winglet operation during high speed change of orientation is not required but rapid changes in craft performance parameters are readily accommodated by electronic means coupled to other control surfaces such as rudders and elevators.
Reorientation of the wing of the within disclosed aircraft will allow a plurality of such craft to be transported by air in a single existing cargo air lifter. Rapid operational availability from a remote airstrip is achieved from this mode of transfer, with no reassembly or rework required for operability.
Actuation of the 90 degree wing to its 0 degree position (or vice versa) may be effected by such simple and reliable means as cranks activated by hydraulic or pneumatic pistons. Cranks and drives will be reciprocal and a common system, or redundant dual systems, used for driving the wing into either orientation. Nesting provisions in the fuselage provide for smooth stream lines over the wing's upper surface in either the 0 or 90 degree positions.
Detail features of repositioning means, fuel management, hydraulic line provisions and other aspects of the unitary, rotatable wing are not primary to this invention. They are mentioned and described herein to illustrate that they are all suporting elements to the primary rotatable wing aircraft, subject and object, of this disclosure.
The present invention provides a high performance aircraft, amenable to both low speed and supersonic flight with a supporting unitary wing having winglet control surfaces, which wing can be commanded to either of two ninety degree opposed positions to meet lift or speed requirements determined by its pilot. A number of features and attributes of such a craft is provided herein, but the primary invention is a rotatable wing aircraft as claimed below.
Moveable wing aircraft are known in the art of aeronautics. NASA's AD-1 and F-8/DFBW, are two examples. Swing wing craft such as that of U.S. Pat. No. 2,673,047, Foldable-Winged Craft by R. A. Scarato, the Pivotal Wing Cruise Missile of U.S. Pat. No. 4,453,426 by Groutage, et al are also examples of this type of vehicle. None of those studied possesses the features or advantages of the within invention.